JPS58188844A - Preparation of m-nitrobenzoic acid - Google Patents

Abstract

PURPOSE:To obtain the titled compound useful as a raw material of agricultural chemicals, pharmaceuticals, dyes, etc. economically, in high purity, by reacting m-nitrotoluene with a gas containing molecular oxygen in the presence of a catalyst, an alkali metal compound and a zirconium compound. CONSTITUTION:The objective compound can be prepared by oxidizing m-nitrotoluene with an O2-containing gas in acetic acid solvent in the presence of a catalyst composed of a cobalt compound and a bromine compound (e.g. cobalt bromide), an alkali metal compound (e.g. bromide, acetate, etc.) and a zirconium compound (e.g. zirconium bromide, zirconium acetate, etc.) at 100-140 deg.C and 1-50atm under the condition to give an exhaust gas having an oxygen concentration of 1-8vol%. The amount of the alkali metal compound is 0.1-2g per 1g of bromine used as the catalyst, and that of the zirconium compound is 0.01-2g per 1g of cobalt used as the catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing m-nitrobenzoic acid by oxidizing m-nitrotoluene with a molecular oxygen-containing gas.

m-Nitrobenzoic acid is a compound useful as a raw material for agricultural chemicals, medicines, dyes, etc., and it is desired to develop an economical production method for producing m-nitrobenzoic acid of good quality.

Up to now, methods for oxidizing m-nitrotoluene to m-nitrobenzoic acid using molecular oxygen-containing gas have been disclosed in U.S. Pat.
Publication No. 31 is known, but all of them involve oxidation at a high temperature of about 140 to 230°C using acetic acid as a solvent, a heavy metal catalyst such as cobalt or manganese, and an accelerator containing all bromine. However, the color tone of the produced nitrobenzoic acid, especially when dissolved in an alkaline aqueous solution, had the disadvantage that the color tone of the solution was not good.

Therefore, the present inventors conducted the following steps in the oxidation of m-nitrotoluene to m-nitrobenzoic acid using a molecular oxygen-containing gas.
With the aim of finding a method for obtaining m-nitrobenzoic acid with a good solution color when dissolved in an alkaline aqueous solution, we carried out extensive studies, and made an alkali metal compound and a zirconium compound coexist in the reaction system together with a known catalyst. It has been discovered that the object can be achieved by carrying out the reaction in a low temperature range of 140° C. or lower, and the present invention has been achieved.

That is, the present invention provides a method for producing m-nitrobenzoic acid by oxidizing m-nitrotoluene in an acetic acid solvent with a molecular oxygen-containing gas in the presence of a catalyst containing a cobalt compound and a bromine compound as main components. The compound and the zirconium compound are present in the reaction system, and 100 to 14
This is a method for producing m-nitrobenzoic acid, which is characterized by oxidizing at 0°C.

The method of the present invention will be specifically explained below.

In the process of the invention, m-nitrotoluene is contacted with a molecular oxygen-containing gas in an acetic acid solvent in the presence of a filter catalyst consisting of cobalt and bromine and an alkali metal compound and a zirconium compound.

The appropriate amount of acetic acid to be used is 0.8 to 3 times the weight of m-nitrotoluene. If the amount of acetic acid used is less than 50.8 times the weight, the oxidation rate will be low (L).1) When the reaction product is cooled, it will become a highly concentrated sludge or solid substance that is difficult to handle and is not satisfactory. It is difficult to stably obtain a target product of high quality. On the other hand, if the amount of acetic acid used exceeds 3 times by weight, the economic burden due to combustion decomposition of acetic acid increases, the volumetric efficiency of the reactor decreases by t, and solid-liquid separation remains dissolved in acetic acid after the reaction. Disadvantages arise, such as an increase in the number of target products that cannot be isolated and a decrease in the one-pass yield of the target product. Although there is no particular problem even if water is present in the acetic acid in an amount of about 5% by weight or less, it is preferable that the water content in the acetic acid is small.

As the catalyst, a catalyst system consisting of a cobalt compound and a bromine compound is used, and these catalyst components are added in the form of the following compounds.

In other words, cobalt compounds can be converted into reactants such as bromide, hydroxide, carbonate, salts of lower aliphatic carboxylic acids such as acetic acid, salts of aromatic carboxylic acids such as nitrobenzoic acid, salts of naphthenic acid, and acetylacetonate. Compounds that are soluble and do not contain counter-1 ions that would interfere with the reaction are suitable.

Examples of bromine compounds include inorganic bromine compounds such as molecular bromine, hydrogen bromide, cobalt bromide, ammonium bromide, and alkali metal bromides, as well as tetrabromoethano, bromoacetic acid,
Organic bromine compounds such as benzyl bromide can be used, but cobalt bromide is also preferred. Adding at least a portion of the bromine compound as molecular bromine has the advantage of shortening the induction period.

The amount of cobalt compound used is preferably such that the amount of cobalt metal used is in the range of 0.05 to 1.0% by weight based on the acetic acid solvent.

If the amount of cobalt catalyst used is less than 0.05% by weight, a sufficient reaction rate cannot be obtained, and if it exceeds 1.0% by weight, the burden of separating the metal catalyst from the target product and the catalyst cost will increase. It is disadvantageous.

As a metal catalyst, cobalt has higher catalytic activity than manganese, and the catalytic activity may be even higher when both are used together, but the color tone of the m-nitrobenzoic acid produced In any case, it is good. Therefore, it is preferable to use only cobalt as the metal catalyst.

The amount of the bromine compound used is in the range of 1 to 10 times the weight of cobalt metal, especially 2 to 6 times the weight of the bromine atom.
A range of times the weight is appropriate.

If the amount of the bromine catalyst used is less than 1 times by weight, sufficient catalytic activity will not be obtained, and if it exceeds 10 times by weight, the contamination of the product by bromine and the burden of catalyst costs will become significant, which is not preferable.

In the present invention, by coexisting an alkali metal compound and a zirconium compound in the reaction system in addition to cobalt and bromine, which are catalyst components, it is possible to improve the color tone of m-dil-lobenzoic acid, which is the target substance, especially in an aqueous alkali solution. improves the color of the solution when dissolved in

Suitable alkali metal compounds used for this purpose include bromides, acetates, hydroxides, carbonates, and the like. The amount of the alkali metal compound to be used is such that the amount of alkali metal used is equivalent to 0.1 to 2 gram atoms per 1 gram atom of bromine used as a catalyst component, preferably 0.5
An amount corresponding to ~1.5 gram atom 1C is suitable. If the amount of afkali metal used is too much within this range, the catalytic activity will decrease, and if it is less than this range, the color tone of the target substance will deteriorate.

The other additive, zirconium compound, is
+4-valent zirconium compounds, such as zirconium bromide, zirconyl acetate, and zirconium acetate, that are soluble in acetic acid and do not contain counterions that interfere with the reaction are suitable. The amount of the zirconium compound used is such that the amount of zirconium metal used is equivalent to 0.01 to 2 gram atoms per gram atom of cobalt used as a catalyst component, preferably 0.
．． An amount corresponding to 0.5 to 0.3 gram atoms is suitable.

If the amount of zirconium metal used is more than this range, the catalytic activity tends to decrease, and if it is less than this range, the effect of improving color tone will be weak, which is not preferable.

The reaction temperature is suitably in the range of 100 to 140°C. 10
At a reaction temperature lower than 0°C, the reaction rate becomes extremely slow, while at a reaction temperature higher than 140°C, the by-product of colored impurities increases, which is not preferable.

As the molecular oxygen-containing gas used as the oxidizing agent, pure oxygen or industrial waste gas can be used, but for secondary purposes, ordinary air or a mixed gas of air and industrial waste gas is suitable.

Regarding the oxygen partial pressure in the reaction system, the total reaction pressure should be in the range of 1 to 50 atm, especially 2 to 40 atm, and the oxygen concentration in the waste from the reactor should be in the range of 1 to 8% by volume. It is preferable to operate the When the reaction pressure exceeds 50 atm, no particular advantage can be obtained, although the equipment cost and the power cost for compressing the molecular oxygen-containing gas increase, and on the contrary, decomposition into carbon dioxide increases. This trend is disadvantageous.

In addition, when the oxygen concentration of υ1 scum exceeds 8% by volume, the iTJ ability of the reactor gas phase to form an explosive gas mixture increases, and from the viewpoint of safety measures, the oxygen concentration of rJl scum exceeds 8 f4.
It is necessary to keep it below r Tsuji%.

The reactor used in the present invention is preferably of a forced mixing type rather than a simple bubble column type. That is, in order to achieve good gas-liquid mixing of the molecular oxygen-containing scum and the reaction liquid, to promote dissolution of molecular oxygen into the reaction liquid, and to ensure smooth contact between the reactants in the reactor, It is preferable to use a reactor equipped with a gas inlet consisting of a large number of pores in the lower part of the reactor, and in which forced stirring is performed using a rotating stirring blade or forced circulation is performed using a circulation pump outside the reactor.

A reflux condenser is provided at the top of the reactor, and the exhaust gas is discharged through the reflux condenser, and solvent acetic acid, unreacted m-nitrotoluene, etc. contained in the exhaust gas are condensed and circulated to the reactor.

As the reaction method, any of a batch method, a semi-continuous method, and a continuous method can be employed, but the target substance of better quality can be obtained in the case of a semi-continuous method or a continuous method.

Note that the method for separating Qi of the target substance m-nitrobenzoic acid from the reaction product mixture obtained by the method of the present invention is to cool the reaction product and optionally further concentrate it.
A suitable method is to crystallize -21-benzoic acid and separate it from the mother liquor into solid and liquid.

The thus isolated m--to-benzoic acid is purified to a desired purity by washing with a solvent and recrystallization if necessary, and dried to obtain a product.

On the other hand, the mother liquor from which m-21 to benzoic acid was separated contains m-2) 0-benzoic acid, citric acid, oxidized intermediate, unreacted raw material,
It contains substances for F7 such as a catalyst, and after the by-product water is distilled and separated, it can be recycled to the reaction system as it is or after an appropriate purification treatment and used repeatedly.

By the method of the present invention described in detail below, m-21 of good quality can be obtained.
・It has become possible to economically produce Kuchian-jikoic acid.

Hereinafter, the present research will be specifically explained with reference to Examples.

Example 1 100 parts of acetic acid (100 parts of m-nitrotolueno
weight times), 4 parts of water, 2.49 parts of cobalt tetrahydride hexahydrate,
0.06 parts of molecular bromine (0.45 parts of cobalt to acetic acid)
iFt%, bromine 2.85 parts by weight relative to cobalt), 2.17 parts sodium acetate trihydrate (1 gram atom times sodium relative to bromine), 0.17 parts luconyl acetate (
Zirconium (0.1 gram atom times as much as cobalt) was charged, the reaction pressure was 14 atm, and the reaction temperature was 115°C.
Then, while blowing a mixed gas of 7% oxygen and 93% nitrogen, 17,100 parts of m-nitrotol was continuously fed at a rate that completed the feeding in 2 hours.

Oxygen absorption started 12 minutes after the start of supply, so the gas to be blown was changed to air, and air was continued to be blown at a flow rate such that the oxygen concentration in the exhaust gas was 8% or less, and after 2 hours, m-nitrotoluene was introduced. was stopped, and after 5 hours, air blowing was stopped.

(After the reaction, the product is cooled to room temperature, solid-liquid separated,
Washing with 200 parts of a water-acetic acid mixture (4:1) and drying yielded 72 parts (yield: 59 mol %) of m-di)-benzoic acid with a purity of 99% or higher.

When 2f of benzoic acid (7)m-=l-o was dissolved in 20 ml of IN-KOH aqueous solution, the solution was slightly yellow and I
The light transmittance at 460 nm in the cjl cell is 91
%Met. Furthermore, the mother liquor after solid-liquid separation of the product contains 30 parts of m-21-benzoic acid, and the water-acetic acid mixture used for egg washing contains 8 parts of m-nitrobenzoic acid. The total yield of aromatic acid was 90 mol%.

Comparative Example 1 When the same reaction as in Example 1 was carried out without adding sodium acetate trihydrate, solid-liquid separation occurred and tcom-21.0
The light transmittance of an alkaline aqueous solution of benzoic acid (l1M'$ 61 mol%) at 460 nm is 38%, and the light transmittance of In-nitrobene is 70%. The combined yield of aromatic acid was 92 mol%.

Comparative Example 2 When a reaction was carried out in the same manner as in Example 1 without adding lerconyl acetate, the light transmittance at 460 parts m of an alkaline aqueous solution of rn-nitrobenzoic acid (yield 57 mol%) separated into solid and liquid was 78. %, the total yield of m-nitrobenzoic acid was 88 mol%.

Comparative Example 3 In Example 1, the reaction temperature was raised to 145°C and the reaction was carried out in the same manner. The transmittance was 62% and the total yield of m-nitrobenzoic acid was 93 mol%.

Comparative Example 4 In Example 1, the reaction temperature was lowered to 95°C and the reaction was carried out in the same manner. However, even when the reaction product was cooled to room temperature, m
-Crystals of nitrobenzoic acid (did not precipitate).

Example 2 In Example 1, the same reaction was carried out using 1.56 parts of potassium acetate (1 gram atom of potassium over bromine) instead of sodium acetate 1, trihydrate. Solid-liquid separation t:m-21-benzoic acid (yield 60 mol%)
The light transmittance at 460 parts m of an alkaline aqueous solution is 90
%, the total yield of m-nidobenzoic acid was 89 mol% and t.

Patent applicant Higashi Shikikai Co., Ltd.

Claims (1)

[Claims] In a method for producing m-nitrobenzoic acid by oxidizing m-nitrotoluene with a molecular oxygen-containing gas in the presence of a catalyst containing a cobalt compound and a bromine compound as main components in an acetic acid solution a, an alkali metal compound and a zirconium compound are used. A method for producing m-nitrobenzoic acid, which comprises oxidizing at 100 to 140°C in the presence of m-nitrobenzoic acid in a reaction system.